Rotary intaglio offset printing machine



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ENGRAl/Eo cYL/NDER IN VEN TOR. M//V//lawz f7. We/'c//fc 7' U19/VE X Unite States Patent O ROTARY INTAGLIO OFFSET PRINTING MACHINE William A. Weidlich, Scotch Plains, NJ., assigner to Interchemical Corporation, New York, NX., a corporation of Ohio Filed Oct. 30, 1956, Ser. No. 619,315

3 Claims. (Cl. 101-154) This invention relates to printing equipment, in particular rotary intaglio offset printing machines, and aims to provide such a machine which gives fine printing results, particularly on irregular rigid objects, which are comparable with results hitherto obtainable only with hand operated transfer rollers, while at the same time providing a machine in which the operating parts have a long life.

Printing of fine designs on irregularly shaped metal objects may be done in two ways-the article may be printed flat, and then deformed; or the article may be printed after deformation, with a soft transfer roller which picks up the design from the printing slate. In the latter cases, small deformations in the metal object are accommodated by the resiliency of the transfer plate, while large deformations require multiple transferring to the object.

In the printing of imitation wood and grain designs on metal pieces such as automobile dash boards, the best results have been obtained by intaglio offset printing. The desired design is etched into a at metal plate, which is inked; the plate is scraped clean with a doctor blade; the ink is picked up by a hand-operated soft transfer roller of soft glue-gelatine, rubber, vinyl plastic or similar ink resistant composition; and the operator transfers the design, by hand, to the somewhat irregularly shaped work piece. The transfer roller is cleaned of ink between each successive impression by the use of a cleaning cloth with ink solvent on it, or by rolling it on absorbent paper.

The inevitable mechanization `of the process, to speed up the work of printing, has resulted in loss in quality. Such mechanization involves the use of engraved rollers rather than plates, and the fixing of the transfer roller in a frame with the engraved roller, whereby the design transfers continuously. The transfer roller is generally driven at the same surface speed as the engraved roller, and the variable braking action of the pieces being printed often causes a slight slur in the transfer of ink.

This variable braking action is a function of the size and shape of the piece being printed, and the pressure exerted between it and the transfer roller. Since the transfer roller is soft and compressible, this variable pressure acts to slow up the transfer roller vis-a-vis the engraved roller, so that they `operate at a slight speed differential, whereby the design slurs slightly as it passes from the engraved roller to the transfer roller.

A second problem which affects quality is that of residual ink on the transfer roller after printing, which will dirty the next print unless it is in exact register (extremely difficult to get with the very soft transfer rollers used) or unless it is removed. Reciprocating doctor blades have been commonly used; if these are sufficiently pressured to remove all the ink, they erode the transfer rollers rapidly, and thus cause loss in quality.

According to my invention, I overcome these diiculties in rotary intaglio offset presses which use soft transfer rollers by using a freely rotating transfer roller, which is driven by one or more metal doctor rollers which ICC operate at exactly the same speed as the engraved plate cylinder. In this fashion, I accommodate the entire machine to the braking action of the work pieces, and avoid the speed-differential slur inevitable when the transfer roller and plate cylinder are both driven. Furthermore, the use of a doctor roller to drive the transfer roller at the speed of the engraved plate cylinder ensures against the slight slur which would be obtained if the plate cylinder alone were driving the transfer cylinder, which slur is due to the slight slippage which must occur because the line of contact between the engraved plate cylinder and the transfer roller is through the full wet ink film which is being transferred. Furthermore, the driving doctor roller removes the ink without erosion of the transfer roller. Normally, one such cylinder is sufficient; but for very fussy work, I prefer to use two such cylinders, to ensure substantially complete removal of ink from the transfer roller.

Obviously, it is necessary to remove the ink from the doctor rollers as they remove it from the transfer rollers. This is done with doctor blades, which scrape the ink from the metal rollers.

The invention can best be understood by reference to the accompanying drawing, which is a schematic lay-out of my press.

Referring to the drawing, I provide a soft transfer roller 10, of glue-glycerine composition, rubber, vinyl plastisol or the like elastic deformable material; preferably its hardness is of the order of Durometer A-20, or lower. This is rotatably mounted on a shaft 11, journaled in the side frames of the press (not shown on the drawing). I may provide an impression cylinder 12, where flat pieces are to be printed; or the impression cylinder may be removed from the press, to print nonplanar pieces, which will be held against the transfer roller by an operator.

The engraved plate cylinder 14 is journaled in the side frames on its shaft 15; it operates in an ink pan 16 containing a body of ink 18 which is picked up by the cylinder 14, excess being scraped off before its contact point with the transfer roller by a doctor blade 26. The plate cylinder is driven from a shaft 20 which carries a worm 22 which contacts a meshing gear 24 attached to the plate cylinder shaft 15.

The shaft 20 also drives the doctor roller 28 through a worm 30 and gear 32 attached to the shaft 29 of the doctor roller 28. A doctor blade 34 bears against the doctor roller 28 and scrapes ink into a pan 36.

Preferably, the doctor roller and the plate cylinder are of identical diameter, to minimize the need for involved gearing to ensure identical surface speed.

In the operation of the device, the roller 28 frictionally engaged and drives the transfer roll 10 at the same speed as the engraved plate cylinder 14. Since the rollers 28 and 14 are mechanically geared to one another, they must operate at the same speed-hence there can be no slur in ink transfer from the engraving to the transfer cylinder. If braking slows the roller 10, it is transferred to both rollers 28 and 14 simultaneously.

Ink from the reservoir 18 fills the engraving, is scraped off by the doctor 28, and transfers to the transfer roller 10. It is then transferred in large part to the work; the residue is largely picked up by the roller 28, and is scraped off the roller by the doctor 34 into the reservoir 36.

A single driving doctor roller is suiiicient for all but the most exacting work. For such work, I may provide an identical second doctor roller A28 driven by a shaft A20 keyed to the shaft 20 in such fashion that the speed of the roller A28 is identical with that of the roller 28. A doctor A34 scrapes excess ink off this roller A28 into a pan A36.

It .will be seenthat I .have'provided an intaglio oiset printing press Which solves the problem of mechanizing the 01d hand transfer press .with minimum loss of quality, in that I overcome slur in transfer from the plate cylinder ,to the transfer cylinder, and in `thatll provide ample cleaning -for the transfer :cylinder by the very devices `that eliminate slur in rtransfer.

Obviously, the specific embodiment of yrny Vinvention described herein can be modied Without departing -from Vrotatably 4mounted-doctor roller in driving kfrictiona'l 15 engagement .with the transfer'rollensaid :doctor roller and yplate cylinder being mechanically `cou-pled for rotation at the same peripheral speed and means -for rotating said doctor roller and plate cylinder at the same periph- V.eral speed.

2. The device of claim 1, in which the engraved plate cylinder and the doctor roller are of the same diameter.

3. The device of claim 1, further including a second doctor roller in driving frictional engagement with the transfer roller, said second .doctor roller and said plate cylinder being Amechanically coupled. for rotation at the same 'peripheral speed, and means for rotating said second doctor roller and plate cylinder at the same peripheral speed.

References Cited in the le of this patent UNITED STATES PATENTS 846,131 Munz Mar. 5, 1907 1,807,963 Casto et al. June 2, 1931 2,016,868 McBean Oct. 8, 1935 

